This invention relates to blast cabinets and in particular to a blast cabinet suitable for use in automated or manual parts cleaning utilizing ice particle blasting media.
Abrasive blasting has been used for many years as a means for removing undesirable materials from objects. In abrasive blasting a high velocity stream of an abrasive blast media, entrained in a gas or liquid stream, are directed at the object to be treated to remove undesired materials. Abrasive blasting is used in applications ranging from cleaning and deburring machined parts to ship hull cleaning. Conventional abrasive blast media include materials such as steel shot, glass beads, aluminum oxide and the like.
Ice blast technology differs from abrasive blasting. For example, ice blasting utilizes a high-speed stream of small ice particles rather than an abrasive blast media to remove undesired materials from an object. Ice blasting is useful for polishing and removing surface contaminants, coatings, burrs and the like. An apparatus and method for continuously delivering ice particulates at high velocity is disclosed in U.S. Pat. No. 6,001,000 which is assigned to the assignee of the present invention, and is hereby incorporated by reference. Ice blast technology has been shown to be highly effective in cleaning due to the scrubbing mechanism of ice particles on impact, and the rinsing mechanism of the spent ice after impact. As a result, many applications emerged for ice blast cleaning. A typical ice blasting apparatus entrains ice particles in an air stream that propels the ice particles at high speed towards the article to be treated. In article cleaning applications, ice blasting can eliminate or reduce the use of environmentally unfriendly cleaning chemicals that might otherwise be used to clean the articles. With increasingly more stringent environmental regulations, many manufacturing and repair shops that routinely use chemicals for degreasing and cleaning of tools and parts are forced to find alternative cleaning methodologies.
While open blasting (i.e. blasting in an open area) is effective for many applications, the open blasting process is noisy and typically produces a lot of blast spray that may contain grease and/or other materials removed from the treated object. Such open blasting is not desirable or practical in certain applications, and may not conform with EPA and OSHA requirements. As an alternative to open abrasive blasting, a blast cabinet is sometimes used to provide an enclosed compartment for performing the abrasive blasting process. For example, automobile manufacturers sometimes use blast cabinets to remove surface applications from improperly painted automobile body parts, prior to repainting. Blast cabinets are also used in cleaning used machine parts that are to be salvaged and/or refurbished.
In conventional blast cabinets an abrasive blasting material is typically entrained in a high-speed gas or liquid jet and directed towards the article to be treated. The kinetic energy of the abrasive blasting material, in combination with the liquid or gas jet, is used to dislodge and/or remove undesired materials from the article, such as dirt, oils, paint, rust or other oxidized layers, burrs and the like. Although conventional blast cabinets are effective for many applications, they have some disadvantages. For example, the abrasive blast media itself must be properly handled. It is often necessary or desirable to recycle the abrasive blasting material, which requires a system for recovering and separating the blasting material from the undesired materials being removed from the workpiece. When friable abrasives are used, the friable abrasives tend to generate a fog-like plume of particulates in the blasting cabinet that can obstruct the user""s view of the workpiece, and create an undesirable work environment.
U.S. Pat. Nos. 5,177,911 and 5,556,324, for example, disclose blast cabinets that use dry abrasives which require dust control and blast media recycling. Such cabinets are not suitable for ice blasting, however, because, 1) the ice particles will accumulate in the blast cabinet over time; 2) ice blast is a generally wet process requiring water-tight and corrosion-resistant construction of the blast cabinet; and 3) the exhaust air produced during ice blasting is moisture laden, and therefore not suitable for direct discharge into a typical shop space. In addition, a portion of the ice blast media (ice particles) will not melt during the blasting operation, and in time can accumulate in a confined blast cabinet.
An ice blast cabinet provides an enclosed environment for cleaning surfaces of an article with an ice blast media is disclosed. The ice blast cabinet includes an enclosure defined by a lower tub-like portion with a drain, a peripheral wall and a top portion. A support for holding the article to be cleaned is provided within the enclosure. At least one ice blast nozzle is mounted within the cabinet and directs a stream of high speed ice particles toward the article. In one embodiment, the nozzle is mounted in the top portion of the cabinet, and directs ice downwardly on the workpiece. A de-icing energy management system in the enclosure is operable to melt any accumulations of ice particles to facilitate removal of the discharged ice blast media from the ice blast cabinet. In an embodiment of the invention, the de-icing system includes heating elements disposed in the enclosure.
In another embodiment of the invention, the de-icing system includes a heat exchanger disposed in the enclosure, wherein a heat exchanger fluid is circulated through the heat exchanger.
In a further aspect of the invention, relatively warm heat exchanger fluid is provided to the heat exchanger to facilitate de-icing, and the cooled heat exchanger fluid is then circulated through an external compressor to provide cooling to the compressor, prior to recirculating the fluid through the heat exchanger.
In another aspect of the invention, ducting is provided through the enclosure, and air is circulated through the ducting to provide air conditioning to an area outside of the blast cabinet.
In an embodiment of the invention directed to automated ice blast cleaning operations, the cabinet has side cut-outs for workpiece part entry and exit on a conveyor with automated speed or motion control. The blast nozzle may be stationary or articulated. For large and/or complex parts, more than one nozzle may be fitted within the cabinet.
In ice blast operation, the phase transitions of ice to water, and water mist to vapor, absorbs a huge amount of thermal energy. The present invention enables utilization of the thermal sink represented by the melting and vaporizing ice blast media, for example to increase the efficiency of the ice making process and/or to cool hot work areas or other machinery.